Infographic on the chemistry of cherries. Cherry colour is due to anthocyanins. Sweet cherries contain primarily cyanidin-3-o-rutinoside, while in sour cherries cyanidin-3-glucosylrutinoside is more abundant. Sour cherries also contain greater concentrations of anthocyanins than sweet cherries. The tart flavour of sour cherries is due to a greater concentration of malic acid; they also contain less sugar than sweet cherries. Like many other stone fruits, the pits of cherries contain amygdalin, a compound which releases hydrogen cyanide when broken down during digestion. You'd need to eat a very large number of pits to see toxic effects, but less is needed for some animals. Other parts of the cherry tree, including the leaves, are also toxic to animals.
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It’s cherry season in the UK, and the cherry trees are currently heaving under the weight of both sweet and sour cherries. Here we take a look at the chemical differences between the two, and why cherry stones are poisonous.

As with many fruits, the colour of cherries is due to the presence of anthocyanins. These compounds have similar structures, though the sugar portion of the molecule can vary, giving a variety of different possible compounds. In sweet cherries the main anthocyanin is cyanidin-3-0-rutenoside, whereas in sour cherries cyanidin-3-glucosylrutinoside is dominant. Sour cherries also contain a greater concentration of anthocyanins, accounting for their usual darker colour.

Anthocyanins are examples of phenolic compounds, and other phenolic compounds that cherries contain include polyphenolics and flavonoids. These compounds have anti-oxidative effects, and as such cherries are commonly touted as a health food. The anti-oxidant compounds act as electron donors, and can inhibit the oxidation of other molecules. Oxidation produces free radicals, molecule fragments that have been linked with involvement in a number of health conditions. However, there is still not strong evidence that anti-oxidants can have a significant impact on most diseases.

One compound in cherries that can potentially affect you, however, is amygdalin. Amygdalin is found in the pits of cherries, and when digested gets broken down, producing hydrogen cyanide. Amygdalin is also present in the pips of several other fruits, including apples and apricots. While you’re unlikely to be eating copious amounts of cherry pits anyway, though cyanide is a well-known poison there’s not too much cause for concern. Cherry pits only contain around 3% amygdalin, and you’d likely need to eat at least 30 crushed seeds in order to experience serious toxicity. Also, the pits pass through your system harmlessly if eaten whole, as the pit does not then get digested.

Amygdalin is actually found in all parts of the cherry plant except the fruit’s pulp, and it can pose a danger to animals. Wilted cherry tree leaves in particular are poisonous to cows, and cases of toxicity and death have been reported.

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References & Further Reading

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